This invention relates to fluorochemical compositions which provide oil repellency and water repellency properties to substrates. This invention further relates to a method for imparting oil- and water-repellent properties to various substrates and the resulting treated substrates.
The tanning of leather is a complex process described, for instance, in the Kirk-Othmer Encyclopedia of Chemical Technology. Fourth Edition, Volume 15, pp. 159-176. Produced from animal skins, leather is used for many purposes, including shoes, upholstery, clothing, gloves, hats, books, sports equipment, and the like. In most such uses, water repellency is desired and conventionally achieved by the application of fats, or by surface treatment of the leather after drying. The application of fat to the leather does not provide any oil repellency. Oil repellency for leather, and thereby soil repellency, is also a desirable property in most of these uses but is more difficult to produce. Limited oil repellency can be obtained by certain surface coatings after the leather has been dried. Such surface applications to dried leather do not penetrate, or penetrate only to a limited extent, throughout the thickness of the leather and thus do not provide significant oil or water repellency in depth through the thickness of the leather. Consequently, when the leather is cut in the manufacture of articles, or when the surface of finished articles is damaged by abrasion in use, the exposed leather is deficient in oil repellency and soil resistance. Additionally, the post-drying surface finishing of leather is an art in itself, and any coatings must be compatible with the final treatments given to leathers in various uses.
Incorporation of oil repellent materials onto the dried leather hides by spraying or into the hides during the wet stage processing, e.g., during the tanning, retanning, and dyeing baths, is practical and in use in the leather industry. However the leather, after drying and processing to produce the desired repellency, either requires a high temperature cure at about 100xc2x0 C. or lengthy storage time (about 2 weeks) at room temperature.
A number of treatment processes have been described for improving the water- and oil-repellency of leather, for instance, Diesenroth, et al, in U.S. Pat. No. 5,693,747 describe sulfur-containing diols capable of being reacted with urethanes to make repellent materials. Certain of Deisenroth""s compositions contain an organic sulfate group, but do not contain sulfonate groups.
It is desirable to provide fluorochemical oil- and water-repellent formulations that are compatible with the wet stages of leather processing, and that would, after drying and fabrication of finished leather products, provide oil and water repellent properties immediately and without a cure step substantially throughout the thickness of the leather. Furthermore, it is desirable that such bath additives be effective with essentially no changes in the leather processing steps, be compatible with leather treatment bath formulations, and be applied without the need for additional equipment. The present invention provides such a bath additive. Further, such compounds provide oil repellency and water repellency to other substrates.
The present invention comprises a polymer having at least one urea linkage derived by contacting (1) at least one polyisocyanate, or mixture or polyisocyanates, (2) at least one fluorocarbon alcohol, fluorocarbon thiol or fluorocarbon amine, (3) at least one straight or branched chain alcohol, amine or thiol, (4) at least one alcohol containing a sulfonic acid group or its salt, and then (5) optionally at least one linking agent.
The present invention further comprises a method of imparting oil repellency and water repellency to leather, wood, masonry and textile substrates comprising contacting said substrate with the polymer described above. The present invention further comprises substrates having oil repellency and water repellency treated with a polymer as described above.
Trademarks and tradenames are indicated herein by capitalization. The present invention comprises urethane-based polymers that can be applied during the wet treatment, tanning, or bath stage of leather processing, providing oil- and water-repellent properties and soil resistance substantially throughout the thickness of the leather. The dispersions are compatible with conventional leather treatment processes without process changes and are superior to surface coating of treated leather. The polymers are also useful to impart oil repellency and water repellency to wood, masonry and textile substrates.
The urethane-based oil- and water-repellent polymers of the present invention comprise branched polymers having at least one urea linkage per molecule and are derived by contacting (1) at least one polyisocyanate, or mixture of polyisocyanates, which predominately contains at least three isocyanate groups per molecule, (2) at least one fluorocarbon alcohol, fluorocarbon thiol, or fluorocarbon amine, (3) at least one branched or straight chain alcohol, amine, or thiol, (4) at least one alcohol containing a sulfonic acid group or the salt of a sulfonic acid group, and (5) optionally sufficient liking agent to react with all remaining isocyanate groups. These are hereinafter identified as Reactants 1-5. By the term xe2x80x9cpolyisocyanatesxe2x80x9d is meant tri- and higher isocyanates and the term includes oligomers.
The polyisocyanate reactant (Reactant 1) provides the branched polymer backbone of the polymer. Any polyisocyanate having predominately three or more isocyanate groups, or any isocyanate precursor of a polyisocyanate having predominately three or more isocyanate groups, is suitable for use in this invention. It is recognized that minor amounts of diisocyanates may remain in such products. An example of this is a biuret containing residual small amounts of hexamethylene diisocyanate. Particularly preferred as Reactant 1 are hexamethylene diisocyanate homopolymers having the structure of Formula 1. 
wherein k averages about 1.8. These are commercially available, for instance as DESMODUR N-100 from Bayer Corporation, Pittsburgh Pa. DESMODUR N-100 is a hexamethylene diisocyanate-based polymeric isocyanate containing biuret groups. While individual homopolymers having k=1, 2, etc., are suitable for preparing the polyurethane polymers of the present invention, this specific homopolymer is only available in admixture with substantial amounts (50% or more) of homopolymers having k greater than 1, i.e., substantial amounts of tetra- and higher polyisocyanates.
Also suitable for use as Reactant 1 are hydrocarbon diisocyanate-derived isocyanurate trimers which can be represented by Formula 2. 
wherein R is a divalent hydrocarbon group, preferably aliphatic, alicyclic, aromatic, or arylaliphatic. For example, R is hexamethylene, toluene, or cyclohexylene, and is preferably hexamethylene, which is available as DESMODUR N-3300 (a hexamethylene diisocyanate-based isocyanurate). Other triisocyanates useful for the purposes of this invention are those obtained by reacting three moles of toluene diisocyanate with 1,1,1-tris-(hydroxymethyl)ethane or 1,1,1-tris-(hydroxymethyl)propane. The isocyanurate trimer of toluene diisocyanate and that of 3-isocyanatomethyl-3,4,4-trimethylcyclohexyl isocyanate are other examples of triisocyanates useful for the purposes of this invention, as is methine-tris-(phenylisocyanate). Precursors of polyisocyanate, such as disocyanate, are also suitable for use in the present invention as substrates for the polyisocyanates.
Preferred polyisocyanate reactants are the aliphatic and aromatic polyisocyanates containing biuret structures. Most preferred is the homopolymer of hexanethylene diisocyanate, DESMODUR N-100.
The fluorocarbon alcohol, fluorocarbon thiol, or fluorocarbon amine (Reactant 2) provides the oil- and soil-repellency and contributes to the water repellency of the polymer. The fluorocarbon alcohol, fluorocarbon thiol, or fluorocarbon amine reactant suitable for use in the present invention has the structure:
Rfxe2x80x94Xxe2x80x94Yxe2x80x94H
wherein
Rf is a C4-C20 linear or branched fluorocarbon chain,
X is a divalent linking radical of formula xe2x80x94(CH2)p or xe2x80x94SO2N(R1)xe2x80x94CH2CH2xe2x80x94, wherein p is 1 to about 20; and R1 is an alkyl of 1 to about 4 carbon atoms; and
Y is xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, or xe2x80x94N(R2)xe2x80x94 where R2 is H or R1.
More particularly Rf is CqF(2q+1) wherein q is 4 to about 20, or mixtures thereof Preferred examples of Rfxe2x80x94Xxe2x80x94 include the following: 1) mixtures of F(CF2)q(CH2)nxe2x80x94 wherein q is as previously defined and n is 1 to about 20, and 2) F(CF2)qSO2N(R1)CH2CH2xe2x80x94 wherein q and R1 are as previously defined. An example of mixture 1) includes the group of formula F(CF2CF2)nCH2CH2OH, wherein n has values selected from 2, 3, 4, 5, 6, 7, 8, 9, and 10, said fluorochemical compounds being present in the proportions shown as compositions (i) or (ii):
The alcohol, amine, or thiol reactants (Reactant 3) contribute to the water repellency properties of the polymer. The alcohol, amine, or thiol reactant suitable for use herein is a straight chain or a branched alcohol, a straight chain or branched amine, or a straight chain or branched thiol. Primary alcohols are preferred since such alcohols are more readily reacted with the isocyanate groups than secondary or tertiary alcohols for steric reasons. Reactant 3 is a branched alcohol, amine, or thiol, or a mixture of branched and straight chain alcohols, amines, or thiols. Utilizing a proportion of branched chain alcohols, amines, or thiols provides a softer finish, probably by adding to the chain disorder. While the molar ratio of branched chain alcohol, amine, or thiol to straight chain alcohol, amine, or thiol is quiet broad, the molar ratio of branched chain to straight chain is preferably in the range 100:0 to 40:60.
Suitable straight chain alcohols, amines, or thiols have the structure H(CH2)xxe2x80x94OH, H(CH2)xxe2x80x94NH2, or H(CH2)xxe2x80x94SH, wherein x is 12 to 20 and preferably 16 to 18, or mixtures thereof. Particularly preferred is the readily available stearyl alcohol (1-octadecanol) having x=18. Optionally, ethoxylates of alcohols may be used.
Suitable branched chain alcohols, amines, or thiols have the structure CyH(2y+1)xe2x80x94CH2xe2x80x94OH, CyH(2y+1)xe2x80x94CH2xe2x80x94NH2, or CyH(2y+1)xe2x80x94CH2xe2x80x94SH wherein y is in the range 15 to 19, or mixtures thereof. An example is ISOFOL 18T, a mixture of branched chain alcohols comprising 2-hexyl- and 2-octyl-decanol, and 2-hexyl- and 2octyl-dodecanol, available from CONDEA-Vista Co., Houston Tex. Optionally, ethoxylates of alcohols may be used.
The reactant comprising the alcohol containing a sulfonic acid group or its salt (Reactant 4) contributes anionic sites to the product polymer, such that the polymer has self dispersing properties and forms stable aqueous dispersions without added surfactants. The alcohol-sulfonate salt has the structure
MO3Sxe2x80x94Zxe2x80x94OH
wherein
M is an alkali metal; amonium; alkyl, dialkyl, trialkyl, or tetraalkyl ammonium; or hydrogen; and
Z is a straight or branched chain alkyl group containing from about 2 to about 10 carbon atoms, or an aryl or alkylaryl group containing one or more aromatic rings and 6 to about 11 carbon atoms.
Preferred is sodium 2-hydroxyethyl sulfonate, commercially available under the trivial name sodium isethionate. Other examples of such hydroxysulfonic acids are ammonium isethionate, 3-hydroxy-1-propanesulfonic acid and its sodium salt, 4-hydroxybenzene sulfonic acid and its sodium salt, sodium 4-hydroxy-1-naphthalene sulfonate, and sodium 6-hydroxy-2-naphthalene sulfonate.
The alcohol containing a sulfonic acid group or its salt (Reactant 4) is not necessarily fully incorporated into the polyurethane. Thus the amount of the alcohol containing a sulfonic acid group or its salt may be slightly lower than the amount added and the amount of crosslinking by the linking reagent will be higher.
The sulfonic acid groups or their salts used as Reactant 4 are advantageous over the sulfates used in the prior art. The sulfates are hydrolyzed at the low pH ranges used in leather treatments, while the sulfonates are not hydrolyzed at these pH ranges.
If reactants 1 to 4 are not present in sufficient quantities to consume all of the isocyanate groups, the remaining isocyanate groups are reacted with a multi-functional linking agent (Reactant 5), thereby linking two or more isocyanate-terminated molecules together and increasing the molecular weight of the product. Typically, a compound containing a hydroxy group is used as the linking agent. While water is the most commonly used linking agent, other multi-functional compounds such as glycols are also suitable for use herein. When a linking agent other than water is selected, a stoichiometric insufficiency is used, as discussed below. A fluorinated diol is also suitable for use herein, such as the structure of Formula 3. 
Such a fluorinated diol, clearly, acts a both a linking agent (Reactant 5) and as a fluorocarbon alcohol (Reactant 2). An example of such a diol is LODYNE 941, available from Ciba Speciality Chemicals, High Point, N.C.
The branched polymers of the present invention are prepared in a suitable dry solvent free of groups that react with isocyanate groups. Organic solvents are employed. Ketones are the preferred solvents, and methyl isobutyl ketone (MIBK) is particularly preferred for convenience and availability. A small proportion of a solubilizing aid such as dimethylformamide, dimethylacetamide, or N-methylpyrrolidone (e.g., 10% of the solvent) increases the solubility of the sodium hydroxysulfonate and is optionally used if incorporation of the hydroxysulfonate is too slow or is incomplete. The reaction of the alcohols with the polyisocyanate is optionally carried out in the presence of a catalyst, such as dibutyltindilaurate or tetraisopropyltitanate, typically in an amount of about 0.1-1.0%. A preferred catalyst is dibutyltindilaurate.
The ratio of reactants on a molar basis per 100 isocyanate groups is shown in Table 1 below:
Thus the linking agent is 0 to 30, preferably 15 to 25. The ratio of straight and branched alcohols, amines, or thiols is as previously specified above in the description of Reactant 3.
Since the equivalent weights of Reactants 1-4 vary according to the specific reactants chosen, the amounts are necessarily calculated in molar ratios. Examples of specific polymer compositions showing weight ratios are shown in Table 2 using the various fluoroalcohol homologue distributions shown in Table 3.
A schematic structures of two specific examples of polymers of the present invention are shown in Formulae 4 and 5. The specific structure of Formula 4 is drawn to show the residues of two hexamethylene diisocyanate homopolymers (having k=1, See Formula 1 above), substituted once with Reactant 2, twice with Reactant 3, once with Reactant 4, and then coupled with water as the linking agent (Reactant 5). Actual Reactant ratios as charged are shown in Table 1 and 2. Formula 5 shows the corresponding structure produced when the optional linking step with Reactant 5 is omitted. Formulae 4 and 5 diagrams are intended only to depict the type of linkages present They do not show actual Reactant ratios, all the structures of the various Reactants, complexities such as molecules containing more than two Reactant 1 residues, or the necessary random distribution of Reactants on the Reactant 1 residue. 
Under rigorously quantitative control, it is possible to prepare the polymers by mixing all the reactants. However, this is not preferred. The preferred and most practical method to prepare the polymers of this invention when reactant 5 is water is first to react Reactants 1-4, and then react the product with an excess of water, thereby avoiding the need for precise measurement of relatively small amounts of water. Similarly, when Reactant 5 is a linking agent other than water, again a stoichiometric deficiency of Reactant 5 is used, such that a small proportion of the isocyanate groups, e.g., 1-2 molar %, remain unreacted. This ensures that no unreacted linking agent remains in the final product. After the linking agent has reacted, a small excess of water is added, ensuring no unreacted isocyanates remain in the final product.
Reactants 1-4 are charged in the desired proportions under dry conditions (for example under dry nitrogen) and typically heated to a temperature of at least about 90xc2x0 C. for 2 or more hours to complete the reaction. The sum of the reactants can be insufficient to react completely the available isocyanate groups, thus providing a driving force to complete reactions with all the alcohol, amine, or thiol reactants. When this initial reaction with Reactants 1-4 is completed, the linking agent is added if isocyanate groups still remain. When the linking agent is water, an excess is added to react with all remaining isocyanate groups and simultaneously to increase the molecular weight.
The reaction mass, containing solvent but no remaining isocyanate groups, is emulsified in a homogenizer without the addition of emulsifying agent or surfactant. The solvent is stripped from the emulsion by evaporation to provide a polymer dispersion, and the dispersion concentration typically adjusted with water to about 20-40% solids by weight, for convenience in handling. The solids adjustment is made to provide a product dispersion having a fluorine concentration of from about 5 to about 10% by weight. Adjustment of the dispersion concentration is not critical. Lower fluorine concentrations in the dispersion will require the use of larger amounts of the dispersion in treating the substrates to produce the desired fluorine level in the dry substrate described below. Conversely higher fluorine concentrations in the dispersion would require less dispersion in the substrate treatment. Optionally, a dispersant such as WITCONATE AOS is added to the dispersion before it is applied to the leather.
This invention further comprises a method of imparting oil repellency and water repellency to substrates comprising contacting said substrate with the dispersions of the above described polymers. Typically, such contacting is by application of the polymer dispersion to the surface of the substrate.
Suitable substrates for the application of the polymers of this invention are divided into two classes, based on the preferred loading of the polymer onto the substrate. Hereinafter, these are described as xe2x80x9cClass A Substratesxe2x80x9d or wood, leather, and masonry substrates, and xe2x80x9cClass B Substratesxe2x80x9d or fibrous substrates. Preferred substrates are Class A Substrates such as leather, wood, pressed or otherwise hardened wood composites, masonry such as stone unglazed porcelain and tile, grout, porous concrete and the like. Suitable substrates for this invention also include blends of Class B Substrates with other fibrous Class B substrates.
xe2x80x9cClass B Substratesxe2x80x9d are fibers, yarns, fabrics, carpeting, and other articles made from filaments, fibers, or yarns derived from natural modified natural, or synthetic polymeric materials. Specific representative examples of Class B Substrates are cotton, silk, regenerated cellulose, nylon, fiber-forming linear polyesters, fiber-forming polyacrylonitrile, cellulose nitrate, cellulose acetate, ethyl cellulose, and paper.
The current invention is firstly a leather treatment product that is applied by spray onto dry or semi-wet hides or is applied during the wet processing, or after completion, of the normal tanning, retanning or dyeing process. It is well known in the industry that repellency treatments for leather require a heat cure or lengthy storage time to develop fully the oil and water repellency. The heat cure in particular can seriously affect the hand or softness of the leather product. The present invention, in contrast to the prior art, does not require such a heat cure or lengthy storage time to develop the repellency properties. This advantage enables fabrication of the leather article immediately after leather drying and processing and eliminates the storage facilities and delay currently needed for development of the functional leather properties. Leather treated with the compositions of the present invention has a xe2x80x9chandxe2x80x9d or softness virtually indistinguishable from the untreated leather. Repellency treatments of the prior art are characterized by a deteriorated hand. xe2x80x9cHandxe2x80x9d or softness of finished leather is a subjective quality, conventionally measured by a panel, members of which are unaware of the identity of the sample being evaluated. Such evaluation techniques are well known to those skilled in the art.
The manufacture of leather provides special opportunities to combine the application of the polymer dispersion with the manufacturing process. During the final stages of leather manufacture, after the tanning steps, the wet leather is typically washed with water in a drum. In the practice of this invention, the water in the drum is adjusted to pH 3.5-4.0 with formic acid or ammonium hydroxide and a temperature of 35-40xc2x0 C. The fluorocarbon dispersion prepared as above is added in an amount sufficient to provide a typical fluorine content of 3-6% based on the finished dry weight of the leather. The leather and dispersion are tumbled for about 0.5-2.0 hours, then the pH is adjusted with formic acid to 3.2-3.5. Tumbling is continued for 10-30 minutes, the wash liquid drained, the leather optionally rinsed, and dried. The higher pH range causes the leather to swell, the lower pH reverses the swelling. The leather may be dried at ambient temperature overnight at typical room temperatures of 65-75xc2x0 F. (18-24xc2x0 C.) or with mild heat to accelerate the drying process. No heat curing step is required. Subsequent softening treatments such as staking and dry milling are performed conventionally.
It will be readily recognized by those skilled in the art of leather preparation that many variations of the final stages of leather treatment are practiced and the description above is provided as an example and is not intended to limit the application of the fluorocarbon dispersion to leather. For instance, the range of 3-6% based on the weight of the leather may need to be reduced for thin leathers and increased for thick leathers. Additionally, leather types vary due to source and treatment. In practice, the drum concentration of the dispersion will be adjusted to the amount sufficient and necessary to provide the levels of oil and water repellency and soil resistance required for the particular type of leather being treated and its end use.
The amount of polymer dispersion applied to the leather is an amount sufficient to provide a dry leather containing at least 0.2, and preferably 0.2-20 g fluorine/m2, more preferably 0.2 to 2.3 g fluorine/m2. Higher loadings increase cost without significant improvements in repellency. The fluorine content of the polymer is known by calculation based on the synthesis, or by analysis of the polymer. Application levels to other Class B Substrates are the same.
The self-dispersing fluorochemical polymeric dispersions of the present invention allow for the treatment of leather in the tanning process. The compositions uniquely combine hydrocarbon, branched hydrocarbon, fluorocarbon and sulfonic acid moieties into a polymer with a branched urethane backbone. These compositions need no external surfactants for dispersion stability, are compatible with the leather treatments, requiring no heat curing or aging for performance, and develop the desired water- and oil-repellency during the conventional ambient temperature drying of the leather. Additionally, the ability to add the dispersion during the wet treatment stage of the leather preparation permits the treatment to be effective substantially throughout the leather thickness, as opposed to surface treatments of the finished leather. Thus water- and oil-repellency is retained when the. leather is cut during fabrication, or when the leather surface is damaged or abraded in use.
The polymers of the current invention are, secondly, polymers for treating Class B Substrates wherein the oil and water repellent properties of the coated fibrous substrate develop when the conventional high temperature cure is replaced with a low temperature cure. By the term xe2x80x9chigh temperature curexe2x80x9d is meant conventional curing at about 165xc2x0 C. By the term xe2x80x9clow temperature curexe2x80x9d is meant a curing at between ambient temperature and 160xc2x0 C.
It should be understood that curing temperatures above the low temperature cure range will also cause the oil- and water-repellency to develop on Class B Substrates. Similarly, the use of elevated temperatures for drying or pressing will also allow oil- and water-repellency to recover. However, the option of the low temperature cure provides a number of advantages. Dye retention is improved and consequently dye use is reduced, energy is saved in the curing step, productivity and dimensional stability of the fibrous substrate are improved, yellowing caused by heat is reduced, and, when the curing is in gas-fired ovens, exposure to nitrogen oxide (NOx) and the resultant discoloration is reduced.
The polymer dispersions are applied to fibrous Class B Substrates, including but not limited to woven and non-woven fabrics made from polyamides, polyesters, polyolefins, cotton, wool, silk, rayon, and mixtures of such fiber compositions, by conventional methods such as padding, spraying, foam, and dipping. The polymer dispersions are also coapplied simultaneously or sequentially with stainblockers, softeners, wetting agents, antistats, and permanent press aids.
The amount of polymer dispersion applied to the Class B Substrate surface is an amount sufficient to provide at least 200 and preferably 200-5,000 parts per million by weight (xcexc/g) of fluorine based on the weight of the dry fibrous substrate. Higher loadings increase cost without significant improvements in repellency.
When applied to such Class B Substrates, a low temperature cure of about 120xc2x0 C. is used to set the coating on the fibers and develop the desired repellency properties. While conventional high temperature curing at about 165xc2x0 C. will develop the desired surface repellency, the high temperature cure can be avoided. The greatly reduced cure temperature provides a number of advantages. Dye retention is improved consequently dye use may be reduced, energy is saved in the curing step, productivity and dimensional stability of the fabric are improved, yellowing caused by heat is reduced, and, when the curing is in gas-fired ovens, exposure to nitrogen oxide (NOX) and the resultant discoloration is reduced.
Alternatively, the polymer dispersions of this invention are applied topically to Class A and Class B Substrates, including carpets, curtains, upholstery fabrics, clothing, wood, masonry, and dry or semi-wet leather by conventional methods such as spraying, padding, or swabbing.
The oil and water repellency ratings give a measure of the theoretical ability of the surface treatment to prevent water and oil from wetting the substrate surface. Test Methods 1 and 2 are generally used to test treated Class A Substrate samples. The tests are basically very similar to Test Methods 3 and 4 for Class B Substrate sample, with slight variations to accommodate the different sample characteristics. Since the surface properties of substrates vary substantially within the Classes, the selection of Test Method is resolved by applying a drop of water to the untreated substrate surface and observing the drop for 30 seconds. If the drop is absorbed (fibrous substrates, porous surfaces such as unglazed ceramics), test the treated substrate by Test Methods 3 and 4. Penetration or wetting of the tested surface indicates failure for that test liquid, otherwise the test is passed for that test liquid. If the water drop in this screening test is not absorbed, as will occur with leather, non-porous stone, etc., test the treated substrate by Test Methods 1 and 2.
Test Method 1. Oil Drop Rating Test for Class A Substrates
The water or oil repellency rating of the leather is the highest-numbered test liquid that will not wet the substrate within a period of 30 seconds. A darkening of the substrate at the liquid-substrate interface while the drop is present on the surface normally evidences wetting of the substrate. This test is intended to measure the intrinsic repellency of the substrate surface and not to simulate actual wear performance in the field.
Beginning with the lowest-numbered test liquid identified in Table 4 below, 3 small drops are placed (approximately 5 mm in diameter or 0.05 mL volume) on the surface of the substrate in several locations. The drops are observed for 30 seconds from approximately a 45 degree angle. If the oil does not wet the surface around the edge of the drop and the drop maintains the same contact angle, a drop of the next higher-numbered test liquid is placed at an adjacent site on the surface and again observed for 30 seconds.
This procedure is continued until one of the test liquids shows obvious wetting of the surface under or around the drop within 30 seconds, or until the drop fails to maintain the same contact angle between the surface and the drop. The oil repellency rating of the substrate is the highest-numbered test liquid that will not wet the surface within a period of 30 seconds.
Test Method 2. Water Drop Rating Test for Class A Substrates
Drops of standard test liquids are placed on the substrate surface and observed for wetting and contact angle. The compositions of the aqueous test liquids are shown in Table 5 below. The water repellency rating, is the highest-numbered test liquid that does not wet the substrate surface using the evaluation methods above.
Beginning with the lowest-numbered test liquid, 3 small drops are placed on the substrate surface in several locations. The drops are observed for 30 seconds from approximately a 45 degree angle. If the water does not wet the substrate around the edge of the drop and the drop maintains the same contact angle, a drop of the next higher-numbered test liquid is placed at an adjacent site on the substrate and again observed for 30 seconds.
This procedure is continued until one of the test liquids shows obvious wetting of the substrate under or around the drop within 30 seconds, or until the drop fails to maintain the same contact angle between the substrate surface and the drop. The water repellency rating of the substrate is the highest-numbered test liquid that will not wet the substrate within a period of 30 seconds.
Test Method 3. Oil Repellency for Class B Substrates
The treated Class B Substrate samples were tested for oil repellency by a modification of AATCC standard Test Method No. 118, conducted as follows. A sample, treated with an aqueous dispersion of polymer as previously described, is conditioned for a minimum of 2 hours at 23xc2x0 C.+20% relative humidity and 65xc2x0 C.+10% relative humidity. A series of organic liquids, identified above in Table 4, are then applied dropwise to the samples. Beginning with the lowest numbered test liquid (Repellency Rating No. 1), one drop (approximately 5 mm in diameter or 0.05 mL volume) is placed on each of three locations at least 5 mm apart The drops are observed for 30 seconds. If, at the end of this period, two of the three drops are still spherical in shape with no wicking around the drops, three drops of the next highest numbered liquid are placed on adjacent sites and similarly observed for 30 seconds. The procedure is continued until one of the test liquids results in two of the three drops failing to remain spherical to hemispherical, or wetting or wicking occurs.
The oil repellency rating of the substrate is the highest numbered test liquid for which two of the three drops remained spherical to hemispherical, with no wicking for 30 seconds.
Test Method 4. Water Repellency for Class B Substrates
The water repellency test determines the resistance of a treated substrate to wetting by aqueous liquids. Drops of water-alcohol mixtures of varying surface tensions are placed on the substrate and the extent of surface wetting is determined visually. The test provides a rough index of aqueous stain resistance. The higher the water repellency rating, the better the resistance of a finished substrate to staining by water-based substances. The composition of standard test liquids is shown in Table 5 above.
Materials
The following materials were used in the examples hereinafter.
18-CROWN-6 is 1,4,7,10,13,16-hexaoxacyclooctadecane, available from Aldrich, Milwaukee, Wis.
DESMODUR N-100 and DESMODUR N-3300 contain hexamethylene diisocyanate homopolymers, the latter having a cyclic structure. Both are available from Bayer Corporation, Pittsburgh Pa.
ISOFOL 18T and 18E are mixtures of branched chain alcohols comprising 2-hexyl- and 2-octyl-decanol, and 2-hexyl- and 2-octyl-dodecanol, available from CONDEA-Vista Co., Houston Tex.
LODYNE 941 is a fluorinated diol of the structure (HOCH2)2C(CH2SCH2CH2Rfxe2x80x2)2 where Rfxe2x80x2 is a perfluroroalkyl group, and LODYNE 921B is a thiol of the structure F(CF2CF2)nCH2CH2SH where n is 2-5. Both are available from Ciba Specialty Chemicals, High Point, N.C.
NUJOL is a mineral oil available from Schering-Plough, Inc., Memphis, Tenn.
WITCONATE AOS and WITCONATE AOK are anionic surfactants containing C14-C16-alkanehydroxy- and C14-C16-alkene sulfonic acids as the sodium salts, available from Witco Chemical Corp., Houston Tex.
TOLONATE HDB is a biuret of hexamethylene diisocyanate available from Rhodia Co., Cranberry N.J.
ZONYL BA is mixed 1,1,2,2-etrahydroperfluoro-1-alkanols, predominately C8, C10, C12, and C14 with small amounts of C6, C16, and C18, available from E. I. du Pont de Nemours and Company, Wilmington Del.
Perfluorooctanesulfamido alcohol is a fluorinated alcohol available as Fluorad FC-10 from Minnesota Mining and Manufacturing, St. Paul Minn.
MIBK is methylisobutlyketone.